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Issue 37, 2012
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The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(II) and Co(II) complexes with oxalate, oxamidate and dithiooxamidate bridges

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Abstract

Six homodinuclear and two heteronuclear complexes TpNpCo–C2O4–CoTpNp (1), TpNpCo–C2O4–NiTpCy (2), TpCyNi–C2O4–NiTpCy (3), TpNpCo–C2O2(NH)2–CoTpNp (4), TpCyNi–C2O2(NH)2–NiTpCy (5), TpNpCo–C2S2(NH)2–CoTpNp (6), TpNpCo–C2S2(NH)2–NiTpCy (7), TpCyNi–C2S2(NH)2–NiTpCy (8) (TpNp = tris(3-neopentylpyrazolyl)borate, TpCy = tris(3-cyclohexylpyrazolyl)borate), were synthesized and characterized by mass spectrometry, electronic spectroscopy and X-ray crystallography. These compounds possess similar molecular structures, with the metal ions linked by bridging oxalate (1–3), oxamidate (4 and 5) or dithiooxamidate (6–8) ions. The heteronuclear nature of compounds 2 and 7 was additionally confirmed by high-resolution mass spectrometry. The magnetic properties of the Co2+ complexes were modelled taking into account zero-field splitting of this ion, yielding D-values for Co2+ in the range −17(1) to −50(1) cm−1. All the metal ion pairs in compounds 1–8 are antiferromagnetically-coupled, with J values between −10.0(1) and −45.0(2) cm−1 (via the exchange Hamiltonian Ĥex. = −21Ŝ2) and |J| increasing in the order oxalate < oxamidate < dithiooxamidate. This tendency can be attributed to greater M–S bond covalency compared to M–N or M–O bonds (M = Co2+ and Ni2+). It was found that this antiferromagnetic coupling of Co2+ and Ni2+ ions through oxalate is more efficient for these tris(pyrazolyl)borate complexes than for similar oxalate-bridged systems with neutral aliphatic amine ligands.

Graphical abstract: The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(ii) and Co(ii) complexes with oxalate, oxamidate and dithiooxamidate bridges

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Publication details

The article was received on 24 May 2012, accepted on 09 Jul 2012 and first published on 10 Aug 2012


Article type: Paper
DOI: 10.1039/C2DT31121F
Citation: Dalton Trans., 2012,41, 11319-11329
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    The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(II) and Co(II) complexes with oxalate, oxamidate and dithiooxamidate bridges

    E. A. Mikhalyova, S. V. Kolotilov, O. Cador, M. Zeller, S. Trofimenko, L. Ouahab, A. W. Addison, V. V. Pavlishchuk and A. D. Hunter, Dalton Trans., 2012, 41, 11319
    DOI: 10.1039/C2DT31121F

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